Detection and quantification of cancer cells or rare cells present in body fluids are regarded as a potential indicator for clinical diagnoses, prognostication, and biomedicine research. For example, circulating tumor cells (CTC) are rare in the blood of patients with metastatic cancer, and it is possible to monitor the response of CTC to adjuvant therapy. To detect and quantify the rare cells present in fluids, the rare cells must be first separated. Thus, cell separation techniques are developed.
Various cell separation techniques are now available, including fluorescence activated cell separation (FACS), dielectrophoresis (DEP) cell separation, separation techniques that employ massively parallel microfabricated sieving devices, magnetically activated cell separation (MACS), and other techniques that uses optics and acoustics. Among these cell separation techniques, FACS and MACS are most often used.
Although it is often used, FACS suffers several drawbacks, including high cost, difficult disinfection, and consuming a great amount of sample. Contrary to FACS, MACS is efficient to obtain a major quantity of the target cells in a short period and reduces the consumption of the sample. However, these cells must be transferred to a slide or an observation platform before they can be observed with a microscope. Such a process of transfer often leads to a great cell loss.
U.S. Pat. No. 5,565,105 discloses a magnetocentrifugation method, wherein charged particles are deposited in a rotor board and a magnetic field is vertically applied to the rotor board, whereby when the rotor board is brought into rotation, the charged particles contained in the rotor board are moved within the magnetic field, and are thus acted upon by Lorentz force to separate from non-charged particles.
U.S. Pat. No. 6,297,062 discloses a method for separating at least one species of biological entities from a sample solution. Each species being a first member of a pair forming group, from a sample solution by contacting the sample solution with a matrix of magnetic particles wherein each magnetic particle in the matrix is coupled to the second member of the pair forming group. The matrix should contain magnetic particles, coupled to several different species of second members of the pair forming groups. When the sample is contacted with said matrix, and each species of biological entities, binds to its specific second member of the pair forming group which is present in a discrete location, from the other entities, and due to the magnetic properties of the magnetic particles, each species may be obtained separately.
U.S. Pat. No. 6,723,510 discloses a method for separating particles with minimized particle loss, wherein a detergent containing matrix beads are bound with a sample containing target particles so as to reduce the loss of the target particles in the separation processes.
U.S. Pat. No. 7,094,354 discloses a microfluidic device provides separation of particles in a liquid sample, particularly, separation of a sample of whole blood into its components for further analysis. Separation into red blood sample has been transferred into a separation chamber with the application of centrifugal force of less than about five times gravity. When blood in the sample, a separation chamber for receiving the sample and separating it into its fractions using low gravitational forces, and vents for removing the air displaced by blood and its fractions.